1. Field of the Invention
The present invention relates to a winding device for winding material webs into winding rolls. The winding device includes a winding bed that has at least two carrying rolls, at least one of which is driven. Furthermore, the present invention relates to a process for winding material webs cut from a main web into winding rolls.
2. Discussion of Background Information
In one of the last manufacturing steps, a paper web must be wound into a winding roll before it leaves the paper factory to reach an end user, e.g., a printing plant. Since in many cases, the paper webs are manufactured with a greater width than the user requires, the webs must be cut to specified or correct widths prior to packaging. In this manner, a plurality of material webs are produced which have to be wound into a plurality of winding rolls.
A very simple principle for the winding of the winding rolls is the so-called "carrying roll principle." In this procedure, the winding roll to be wound is positioned in a winding bed that includes at least two rolls, of which at least one is driven. The driven roll acts on the circumference of the winding roll to provide the winding. The required nip pressure can be exerted by, e.g., a press roll that presses the winding roll, at least at the beginning of the winding process, into the winding bed. The carrying roll principle is sufficient for many intended uses, and the carrying roll roller utilized in this procedure has a relatively simple design and, therefore, can be produced inexpensively.
In recent times, there has been a trend toward wider rolls. However, with increasing roll width also comes increasing roll weight. The weight of the winding roll has considerable influence on winding tightness because the force due to the weight of the winding roll on the support face determines the nip pressure. Normally, winding tightness should decrease from the inside of the winding roll toward the outside. However, with a winding roll with excessive weight, the course of the winding tightness is exactly the opposite, i.e., tighter on the outside of the roll than inside, which causes problems. In this manner, occasional tube errors occur, e.g., paper layers on the interior of the winding roll shift axially. Occasionally, a rupture of the paper web is also observed on the interior of the winding roll. These and other phenomena lead to damaged or at least almost damaged winding rolls, which should be prevented.
To better control the course of the winding tightness, an alternative procedure, i.e., the so-called "support roll principle," has been developed. Here, the winding roll is secured centrally, i.e., at its winding core, and is rotatably driven. A press roll, which can also be driven, contacts the circumference of the winding roll so as to control the course of the winding tightness. Deflection of the winding roll, which is to be expected with greater roll widths due to the length of the winding roll causing sag in the middle of the winding roll, is compensated for by providing a support roller underneath. However, a support roll roller is much more expensive, which correspondingly increases production costs. This is exacerbated by the fact that, because the winding rolls are secured on their end faces, the individual winding rolls can no longer axially adjoin one another directly, an arrangement that is possible with a carrying roll principle. Thus, winding rolls whose roll cores are arranged on a common imaginary axis must have an axial spacing from one another so that the devices engaging the roll core have enough space available to operate.